Hydrothermal synthesis and electrochemical characterization of novel zeolite membranes supported on flat porous clay-based microfiltration system and its application of heavy metals removal of synthetic wastewaters

The present work describes the synthesis and characterization of a zeolite type LTA-clay composite membrane on pre-existing locally organized aluminosilicate in clay support and its application to the removal of heavy metals. X-ray diffraction reveals that the natural clay consists essentially of quartz, kaolinite, illite, dolomite, and calcite phases. Flat discs, membrane supports are prepared by uniaxial pressing of natural clay with 160 ≤ Ф < 250 μm as optimal grain size mixed with 3% w/w activated carbon as porogen agent. Membrane supports are consolidated by sintering to final temperatures of 1000 °C. Zeolite Linde type A (LTA) is deposited on the clay supports using the hydrothermal method. Nitrogen adsorption analysis of the support using Brunauer–Emmett–Teller (BET) theory showed pores with 35.5 nm, which is narrowed to 14.2 nm after zeolite-A deposition. X-ray analysis of the composite membrane (MZA) reveals the growth of new diffraction peaks characteristic of zeolite-A. Prior to water filtration analysis of the MZA composite membrane, the pzc is found to be 9.8 using the titration method. The efficiency of the MZA composite membrane is evaluated by filtration tests of solutions containing heavy metals using a flow loop developed specifically for dead-end filtration. The retention of heavy metals studied follows the order Pb²⁺> Al³⁺ > Co²⁺ > Cd²⁺ > Zn²⁺ with 99.7, 99, 89.5, 88.3 and 81.8 retention percent, respectively. The retention mechanism seems to be controlled by the charge of the membrane's surface, which is demonstrated using the linear wave anodic stripping voltammetry (LWASV).